Establishing design principles for functional additives in antimony chalcogenide solar cells

Abstract

Antimony chalcogenide solar cells are a promising thin-film solar technology, offering a tunable bandgap, high intrinsic stability, and a large absorption coefficient. Their solution-processability enables the straightforward incorporation of chemical additives. While many additives have been explored, their underlying chemical mechanisms remain poorly understood. In this study, we examine the chemical mechanism of a proven additive, EDTA, and leverage these insights to develop a screening process for identifying additives that match or surpass its performance. Our findings reveal a dual role of EDTA and similar molecules: (i) Sb³⁺ chelation, enhancing Sb₂S₃ film quality, and (ii) pH reduction in the precursor solution, suppressing Sb₂O₃ formation. Additionally, we propose a chemical mechanism for the in situ conversion of Sb₂O₃ to Sb₂S₃. These insights will aid in the rational design of future additives and establish general guidelines for optimizing the growth conditions of efficient antimony chalcogenide solar absorbers under widely used hydrothermal conditions.